Tablets and capsules are the most common dosage forms for the oral administration of nutritional, medicinal, or other therapeutic products. It is well known, however, that these dosage forms are unacceptable for use by people who have difficulty in swallowing tablets and capsules and that the difficulty is exacerbated by larger tablets and capsules and, in some instances, by the bad taste of the medication. It is generally accepted that these types of problems with medications are serious because they may lead to a failure on the part of patients to comply with the medication regimen ordered by the physician.
The common alternatives to conventional tablets and capsules are chewable tablets and aqueous or hydroalcoholic liquids such as syrups, suspensions and elixirs. Such dosage forms are commonly used for analgesics, cough and cold medications, antibiotics, vitamins and many other nutritional or medicinal products. In general, these forms do not significantly improve the taste of a medication or make it easier to swallow larger doses. For example, therapeutic agents in either chewable tablet or suspension form are generally disliked because they are gritty, astringent and leave an unpleasant aftertaste. Oils, such as mineral oil, fish oils, cod liver oil and castor oil, are usually taken in large doses and, since they are greasy and unpleasant to take, some method must be found to make them easier to ingest. In the past this problem has been dealt with by encapsulating the oils in soft gelatin capsules or by emulsifying the oils in oil-in-water emulsions. These solutions have not been completely satisfactory.
The problem with encapsulation is that, since the maximum size soft capsule that can be ingested contains only about one gram of oil, the ingestion of many such capsules is required when the dose of the oil is large. In the case of fish oil the dose is about five grams a day or more, and the doses of cod liver oil, castor oil, and mineral oil are even larger. The problem with emulsification is that bottles of oil-in-water emulsions of oils are subject to deterioration as a result of attack by microorganisms or oxidation by the air to which they are continually exposed and thus have a limited shelf life. Oils and oil-soluble active agents are frequently vulnerable to oxidation. The integrity of oils, such as fish oil containing Omega 3 fatty acids, and the vitamin potency and unsaturated fatty acid character of oils, such as fish liver oils, are all susceptible to attack by oxidation.
Although aerosol packaging has found high consumer acceptance in many areas, including pharmaceutical products such as inhalants, it has not heretofore been considered for use in formulations requiring a high concentration of suspended solids, i.e., greater than 5 to 13%, because a high solids content usually causes malfunctioning of the aerosol valve. It is neither economical nor practical to dispense active solid agents in the very dilute formulations which would be required for dispensing through an aerosol valve. Moreover, such dilute formulations usually produce an uncontrollable and unmeasurable spray, thereby making it difficult to control or measure the amount of the formulation being dispensed. A further difficulty with aerosol packaging is that most aqueous aerosol solutions would be unacceptable for dispensing active solid agents because the dissolution of the active ingredient prior to ingestion could reduce its bio-availability and also produce an unpleasant taste.
British Pat. No. 1,121,358 discloses an aerosol foam composition for dispensing an oral medication, but is specifically limited to compositions which are oil-in-water emulsions. Furthermore, the composition is either devoid of dispersed solid particles or contains a very minimal solids content, less than one percent. It is believed that the presence of water in the emulsion not only reduces the ability of the composition to hold particulate solids, but also introduces stability problems resulting in shorter shelf life.
There are several prior art patents which presumably disclose anhydrous aerosol foams. For example, U.S. Pat. No. 3,135,658 teaches a method of treating bovine mastitis with a medicated, pressurized, self-propelling, milk-miscible oleaginous liquid composition which foams only after it enters the udder and contacts the natural foaming agents of the milk. It does not teach any type of dosable or meterable foam. Furthermore, the composition is inedible or at least unpalatable.
U.S. Pat. No. 3,770,648 discloses an anhydrous aerosol foam composition for external use which incorporates a silicone resin in a solution of organic solvents to produce a stable "quick breaking" foam when the foam is rubbed into or spread over a surface on which it has been deposited. This patent does not disclose any anhydrous foam products which are suitable for ingestion. It also does not teach any type of dosable or meterable foam for dispensing high concentrations of solid therapeutic agents.
U.S. Pat. No. 3,849,580 discloses an aerosol dispensing system which delivers non-aqueous butter-like edible fat compositions in a foam form. These foams contain no foaming agent and are intended to be used as food spreads.
U.S. Pat. No. 3,929,985 teaches a medicated aerosol foam composition for introduction into the vagina for the treatment of vaginitis, but the composition is devoid of any dispersed solid particles and is inedible or at least unpalatable.
U.S. Pat. No. 4,425,164 teaches the preparation of an aerosol spray cookware lubricant composition similar to the product which is commercially available in food stores under the trademark "PAM". This spray is formed from a mixture of a vegetable oil solution of an emulsifier (lecithin) in admixture with at least 10%, preferably 20 to 30%, of a hydrocarbon propellant and up to 15%, preferably 3 to 10%, of suspended flour or starch particles. The resulting product is a spray in which the particles serve as a visual indicator that the spray is being uniformly applied to the cooking surface. There is no disclosure or suggestion of a directly ingestible stable foam product capable of yielding repeatable, measurable quantities of an active agent from an aerosol container.
Other disclosures of vegetable oil, lecithin-containing edible aerosols (U.S. Pat. Nos. 4,188,412 and 3,821,007) also indicate that such materials are sprays rather than foams. These patents additionally teach that foaming action would be undesirable in such a product.
U.S. Pat. No. 4,174,295 teaches the preparation of a pharmaceutical aerosol containing glycerides or monostearates.